7. Nimue

In flashbacks taking place 1,033 years prior, Merlin drank from the Holy Grail, begetting his transformation into a wizard who is able to heal the forlorn of his village, thus becoming a Christ-like figure. He meets a distraught woman by the name of Nimue, whose village and family were slaughtered by a mongol named Vortigan. Over time the two fall in love, but Merlin's immortality is an obstacle. They set out on a journey to forge the grail into a sword, that will cut away his immortality. Using the Promethean Flame, Merlin conjures Excalibur, but Vortigan attacks them, apparently killing Nimue.

However, Nimue had also drunk from the grail. Citing her newfound ability to take vengeance, she kills Vortigan, becoming the first Dark One, and breaks the sword into two pieces. Meanwhile, in Camelot, Merlin and Emma set out on a journey to speak with the first Dark One and claim the Promethean Spark; while Zelena double-crosses the heroes and joins forces with Arthur. Zelena imbues Merlin's name to the broken Excalibur, and Arthur uses it to command the suddenly enslaved Merlin to do his bidding.